The Honda K20 4-Cylinder is one of the most popular engines ever built. It’s easy to see why, as Honda truly distilled the best parts of their previous engines into a single, robust, package. In addition to the use of performance VTEC on a number of K20 engine variants, every variant is also extremely resilient and can withstand an insane amount of power compared to its factory output. The K20 is beloved for its high-strung character and its ability to rev to the moon and back. The K20 DOHC 4-Cylinder is such a good engine that it is one of the most popular engine swap options outside of the famed Chevy LS.
While the K20 is a fantastic engine in factory form, most people find that they eventually want some more power. That is where forced induction enters the picture. The K20 is notorious for its ability to withstand a high amount of boost and abuse. While some 2.0L K20 owners opt to go the turbocharged route, others looking for a more even and predictable power and torque curve prefer superchargers. Supercharged K20s can easily surpass the 300-horsepower threshold with very few modifications.
In this guide, we’ll cover what it takes to build a supercharged K20 of your own. There are some K20 engine variants that handle a supercharger better than others. However, the overall process applies to every variant in the K20 line.
How Much Power Can a Supercharged K20 Handle
One of the most appealing attributes of the Honda 2.0L 4-Cylinder is its ability to absolutely tank boost. While that might sound like an exaggeration, it really is true. In fact, most K20 variants are able to withstand at least twice their factory horsepower figure reliably. With the introduction of forced induction from a supercharger, a K20 is able to comfortably run anywhere from 320-350 horsepower with unparalleled reliability and with completely stock internals. No upgrades are required.
Of course, there are other considerations that factor into the peak horsepower figure for a K20. While it is always fun to think about the absolute horsepower ceiling, that figure is only useful if the engine doesn’t explode on the first drive. Perhaps most significant is the K20 supercharger tune that you opt to run. One of the K20’s primary weak points when it comes to reliability is the piston ring lands which do not respond well to detonation, as with most other vehicles. With that being said, it is important to think about a safe tune and fueling mods if you are intending on pushing a lot of power. For power goals in the 370-500 horsepower range, you’ll almost certainly need to upgrade your K20’s bottom end with forged internals.
Honda 2.0L 4-Cylinder: Turbo vs Supercharger
When considering forced induction on a K20, most people end up struggling to decide between a K20 turbo setup or a supercharged K20 setup. While there are benefits to each method, supercharging a Honda 2.0L 4-Cylinder tends to be more cost-effective and easier to install. While supercharging might be the way to go if budget and ease of installation are paramount, turbo K20 engines tend to produce more power with slightly less boost.
One of the most important differentiators between the two methods of K20 forced induction is the shape of the power band. Of course, with a K20 turbocharger, power will peak at a part of the rev range that corresponds to the turbo’s spool time. Smaller K20 turbos will reduce the lag time, but there will still be a delay. Due to the fact that K20 superchargers are belt driven, there is no delay in power delivery. Overall, a supercharged K20 will deliver power in a much more linear way than a turbocharged K20 engine. Some people prefer the anticipation that comes with a turbo, while some people like the predictability of a supercharger. It really boils down to personal preference.
Beyond power delivery differences, there is also a power ceiling in terms of how much performance you can squeeze out of a K20 supercharger. Most members of the K20 community claim that 400 horsepower is close to the maximum amount of power that you’ll be able to achieve from a supercharged K20. In contrast, there are turbocharged K20s running close to the 4-digit horsepower mark, obviously with extensive modifications. Considering price, power delivery, and ease of installation is key in deciding which path is right for you.
Best 2.0L Honda K20 Engine To Supercharge
Over the course of the K20’s production, Honda released the 2.0L 4-cylinder in 4 different variants with over 20 different sub-variants. The main K20 variants include the K20A, K20B, K20C, and K20Z. While all of the variants share a very similar overall construction, they also differ in a few key ways that can affect supercharged K20 performance.
For example, compression ratios differ significantly between K20 variants and even differ within their own subvariants. Generally speaking, lower compression is favorable for supercharged K20 applications, as it limits the risk of internal detonation. However, higher compression is generally favored for an elevated horsepower number. Flow characteristics also vary significantly between K20 variants, as some K20 cylinder heads feature higher flow figures than others.
Not all K20 variants feature performance VTEC either. What is referred to as “performance VTEC” is Honda’s variable valve timing system that functions on both the intake and exhaust sides of the engine. While some K20 variants feature the performance version of VTEC, others only feature VTEC on the intake cam. The performance VTEC and supercharger combination will unquestionably provide the best performance. But, you’ll have to make sure to use the right cylinder head for it.
At the end of the day, all of these factors are directly related to their cylinder head. Due to the fact that the bottom end of each K20 variant is identical, you can swap on a cylinder head from a more preferable K20 engine to achieve better results. Cylinder heads from the superior 2.4L Honda K24 engine can also be swapped onto a K20 bottom end.
Supercharged K20A2 / Supercharged K20Z1
While it is possible to supercharge any of the engines in the 2.0L engine family, the K20A2 is arguably the best to supercharge out of the gates due to its widespread availability in the US, its use of performance VTEC, and its high-flowing cylinder head. While the JDM K20A is the holy grail of the K20 engine family, it can be hard to find one in the States. The K20A2 engine is the closest thing that we have to the high-performance K20A stateside.
You could also argue that the K20A2 is the better option anyway due to its lower 11.0:1 compression ratio. The Honda K20A2 engine can be found in US-spec Acura RSX Type S cars. The K20A2 engine tends to be an inexpensive engine to source due to its availability. Once again, if you have another K20 variant, like a K20A3, you can easily swap a K20A2 head onto the bottom end.
The K20Z1 is a runner-up option when it comes to the best K20 variant to supercharge. The Z1 engine is almost identical to the K20A2 found in the earlier version of the Acura RSX Type S. The K20Z1 simply has slightly more aggressive cams. The difference in cams results in the 10 horsepower increase between the A2 and Z1. Overall, the K20Z1 might be the more rewarding engine to supercharge. However, they are often significantly more expensive to purchase than a Honda K20A2 engine.
Supercharged K20 Engine Considerations
Compared to many other engines, the Honda K20 engine is a relatively no-fuss engine when it comes to forced induction. While some other engines require a complete internal rebuild before a sustainable supercharger build can be obtained, the K20 can be largely left alone. In many ways, supercharging a Honda K20 is by far the easiest path to forced induction. Most of the modifications suggested for a supercharged K20 build revolve around exhaust modifications to help the 2.0L 4-Cylinder breath better under load. Even then, those modifications still aren’t required.
Supercharged Honda K20 Exhaust Modifications
Two of the most common modifications recommended to K20 owners looking to supercharge their Honda are headers and corresponding exhaust. Most of the exhaust restrictions found on K20-equipped Hondas and Acuras can be found at the exhaust manifold. K20 headers designed to improve exhaust flow and increase exhaust pulse velocity can be a game changer when paired with forced induction.
4-2-1 headers tend to be the most popular option in the supercharged K-series community. That simply means that four primary tubes merge into two central tubes and then into a single collector. 4-1 headers don’t seem to be as popular. However, it could be argued that they are the better option if top-end power is your main priority. Headers might yield a 15-20 horsepower increase on a naturally aspirated engine. However, they can yield 20-25 horsepower when paired with a supercharger.
Along similar lines, a less restrictive exhaust system can significantly enhance the performance of your supercharged K20 as backpressure can rob horsepower and hinder performance. While there is a lot of debate surrounding the best diameter exhaust to pair with a supercharged K-series, most people either settle for a 2.5” or 3.” As long as the engine is able to breathe better than it did with the stock exhaust, either size should work fine.
Outside of exhaust upgrades, transmission upgrades are another very important aspect to consider. Generally speaking, K-series transmissions are pretty rugged and can withstand a fair amount of abuse. In most cases, a K-series transmission failure results from how the car is being driven rather than the amount of power or torque that the car is making. However, many supercharged K20 owners prefer the 6-speed manual transmission out of a 2002-2006 Acura RSX Type S due to its superior gearing. The 6-speed can generally sustain more power and torque than the 5-speed found in 2002-2005 Civics.
There are also a lot of conflicting opinions in terms of how much torque a stock K-series clutch can handle before slipping. Most K20a forum members agree that a new K-series clutch can hold up very well in some demanding circumstances. Quite a few reports claim that a new stock K20 clutch can hold up against around 250-270 lb-ft of torque and around 350 horsepower. Beyond that threshold, you’ll likely want an upgraded aftermarket clutch. The Competition Stage 2 Clutch is a common option for K20s running over 400 horsepower.
One of the main priorities when supercharging a K20 is keeping the IATs low. Not only does a lower intake air temperature improve overall performance, but it also ensures that your K20 is safe from detonation. If IATs get too high, damage can be done over time. One of the easiest ways to mitigate that issue is to run high-octane gas like E85 or methanol. Both E85 and methanol help to reduce combustion temperatures by burning more efficiently than standard pump gas.
In general, E85 and E85 blends are the better options for increased performance. It helps the engine run cooler internally, reduces the risk of detonation, and has a rating of 108 octane. Power gains can be massive even on small blends of E85. The downside is that E85 is less fuel efficient and puts a higher demand on the fuel system. With that being said, E85 is not the best option in terms of engine safety. That award goes to methanol injection.
Methanol injection significantly reduces the chance of detonation or knock, making high horsepower builds much safer and more reliable. That is the case for supercharged K-series engines as well. Due to the fact that Honda K20 engines rev so high, methanol is a good way to reduce internal temperatures. Methanol injection becomes crucial for high horsepower builds pushing a lot of boost.
Best K20 Supercharger Kits
Since superchargers are such a popular modification for the K-series platform, it’s no surprise that there are quite a few options out there as far as K-series supercharger kits are concerned. As with pretty much any aftermarket system, K20 supercharger kits can range in price anywhere between $3,000 to $8,000. Of course, if you aren’t looking to make a weekend warrior 600+ horsepower K-swapped Integra, chances are that you won’t need to venture into the high end of that spectrum.
Higher price points typically correlate with higher power potential. It is also generally representative of build quality and the type of supercharger that comes in the kit. Some kits make use of a roots-style supercharger, like the TVS supercharger kit, while others feature a centrifugal supercharger design.
1) MercRacing K20 Supercharger Kit
Purchase Here: mercracing.net
The MercRacing K20 supercharger kit is one of the most popular kits on the market. The power potential from the Eaton twin vortices-style supercharger is extremely high and one can perform at a high level. In comparison to other Rotrex-style K20 supercharger kits, the MercRacing TVS kit maximizes the amount of horsepower that you can squeeze from a supercharged K20 without sacrificing daily drivability.
As we covered earlier, this kit will likely provide the most linear powerband of all of the supercharger options on this list. Twin vortices superchargers tend to provide the steadiest power delivery of all of the K20 supercharger options. That means that power and torque are on demand at most points in the rev range. With the right tune and fueling modifications, the MercRacing MR2300 K20 supercharger kit is capable of producing up to 500 horsepower. Compared to other supercharger styles, the K20 TVS supercharger has a decreased blower rpm speed, keeping IATs and internal strain low. The MercRacing roots supercharger kit is one of the most reliable kits on the market because of that as well.
While the MercRacing kit is unquestionably one of the best K20 supercharger kits on the market, there are some other considerations to take into account before pulling the trigger. While the kit does come with an air-to-air manifold, you’ll still need to source an intercooler. Additionally, MercRacing provides a disclaimer saying that the 2300 kit produces too much torque for a stock K20 transmission. A built transmission and upgraded clutch are a requirement for the TVS system.
2) CT Engineering K20 Supercharger Kit
Purchase Here: hardmotion.com
Like the MercRacing kit listed above, the CT Engineering K20 supercharger kit uses an Eaton-style supercharger. As such, the CT Engineering K-series supercharger kit acts very similarly to the MercRacing kit. Both have similar power delivery and boost characteristics. With that being said, the CT Engineering kit can’t touch the MercRacing kit in terms of power potential. That primarily boils down to the CT Engineering’s smaller capacity supercharger.
While CT Engineering states that their K-series supercharger kit is good for around 60-70 extra horsepower while remaining in an extremely reliable state, some K20 owners have been able to squeeze 400 horsepower out of an engine using the kit. Obviously, those cases are the outliers, with most CT Engineering kit owners shooting for the 300-horsepower mark. CT Engineering offers their K-series supercharger kit in either a stage 1 or stage 2 configuration. The stage 1 kit is good for around 240-260 horsepower at 5-6 psi. The stage 2 kit comes with a larger 3.15” pulley and high-performance injectors that raise horsepower to the 280-295 ballpark.
One of the kit’s strong suits is its price. At $4,195.00, the CT Engineering K-series supercharger kit is certainly the best bang for your buck on this list. Despite the lower pricepoint, the kit doesn’t sacrifice build quality or reliability. In addition to the Eaton-style supercharger head unit, the CT Racing kit also comes with cast aluminum supercharger manifolds, all of the necessary mounting brackets, and all of the necessary hardware to install the kit. The CT kit truly is a plug-and-play option and is nearly ready to roll right out of the box. Of course, you’ll also need a tune. Two suggested options are either a HONDATA KPro or a HONDATA reflashed ECU.
3) Kraftwerks K20 Rotrex Supercharger Kit
Purchase Here: hardmotion.com
Moving away from roots-style blowers and onto a more modern K-series supercharger solution, the Kraftwerks K20 Rotrex supercharger kit makes use of a centrifugal design, meaning that it is belt driven. Unlike a roots design, a K20 centrifugal supercharger acts very similarly to a turbocharger. They make use of an impeller to compress intake air which is then forced into the engine. Since a K20 Rotrex supercharger uses a belt to operate, performance is directly linked to engine speed. As a result, kits like the Kraftwerks K20 Rotrex don’t provide as much power low in the rev range as they do in high RPMs.
This has a direct effect on power delivery as well. As performance increases as engine speed increases, centrifugal K20 superchargers tend to have a peaky power and torque curve. That is somewhat similar to how a turbocharger delivers power. Like with a turbocharger, some people like the feeling of having power come on in a direct way high in the rev range. It can be extra fun when paired with an engine like the K20. The high-rpm supercharger performance pairs well with the onset of VTEC at the top of the rev range as well. Typically, a TVS-style supercharger is your best bet for a track-focused build due to the power delivery. However, a Rotrex K20 supercharger can be a good option for the drag strip.
Most of the K20 Rotrex supercharger systems, including the Kraftwerks K20 supercharger kit, are centered around a C30-94 Rotrex head unit which provides some pretty serious power potential. With the right tune, fueling modifications, and exhaust upgrades, the Kraftwerks kit will get you close to the 400-horsepower mark.
Honda K20 Supercharger Kit Guide Summary
The Honda K-series is one of the most beloved 4-cylinder engines ever released. The high-revving, VTEC-touting, 2.0L engine is an extremely impressive engine even in factory form. It is obvious that the K20 was designed with strength and reliability in mind. That is obvious as they are able to withstand double their factory horsepower figure with stock internals. The K20 is the perfect platform for forced induction as a result. The linear power delivery that a supercharger can provide is a standout reason for many. Superchargers tend to be less expensive and easier to install on a Honda K20 as well.
Before installing a supercharger on your Honda K-series, it is important to consider the supporting modifications that you’ll need as well. In comparison to a host of other engines, the K20 barely needs any additional work. That is unless you are aiming for extremely high horsepower figures. K20 exhaust modifications aren’t necessarily required. With that being said, performance headers and an upgraded exhaust will increase engine breathability and horsepower as a result. You’ll also unquestionably need some form of upgraded engine management, the most popular option being the HONDATA KPro. While K-series transmissions can hold up pretty well up to around 300 horsepower, you might need a new OEM clutch around that threshold.
There are three frontrunners in the K-series supercharger kit game, each with its own unique benefits. The MercRacing Eaton-style supercharger kit is unquestionably the best option if high horsepower is the goal. For another twin vortices style K20 supercharger kit, the CT Engineering kit is a great budget-friendly option. Finally, the Kraftwerks Rotrex supercharger kit is one of the most popular K20 centrifugal supercharger kits on the market. Whichever kit you choose, it’s almost impossible to be disappointed by a supercharged Honda K20.